Researchers point at the importance of emotions and its study in mathematics education. This research examines middle school students' emotions during learning mathematics outdoors using the mobile phone. The constant comparison method was used to analyze 30 middle school students' emotions while carrying out 15 outdoor activities using the mobile phone. The research findings indicate that the mobile phone environment where students work outdoors on everyday life activities is an environment where mathematics students cultivate positive emotions towards learning mathematics. This could be done by preparing new and varying types of mathematical problems or activities, as well as new learning environments. Further, the research findings indicate that students have positive emotions when they have the opportunity to explore math ideas and when they have different learning roles, from which they can choose their own. In addition, what influenced the students' emotions most were the task conditions, the outer environment conditions, and the student's condition and perceived characteristics. (Contains 1 table.)